This is caused by a design change compared against TTD/OpenGFX1 which cover the entire tile with dirt to prevent them required being base-terrain aware.
Personally, I appreciate the intention but this change would also belong to the "OpenGFX2+ Houses newgrf" bucket brought up in #95 (comment) moreso.
Additionally, this change makes them affected by #170.
This is caused by a design change compared against TTD/OpenGFX1 which cover the entire tile with dirt to prevent them required being base-terrain aware.
Personally, I appreciate the intention but this change would also belong to the "OpenGFX2+ Houses newgrf" bucket brought up in #95 (comment) moreso.
Additionally, this change makes them affected by #170.